Process for producing hollow viscose filaments



y 0, 1958 lCHlRO KOSUGE 2,835,551

PROCESS FOR PRODUCING HOLLOW VISCOSE! FILAMENTS Filed March 29, 1956F/EE.

United States Patent PROCESS FOR PRODUCING HOLLOW vrscosn FILAMENTSIchiro Kosuge, Kitazono-ryo, Otsu-shi, Japan, assignor to Toyo RayonCo., Ltd., Tokyo, Japan, a Japanese com- P y Application March 29, 1956,Serial No. 574,836

Claims priority, application Japan April 9, 1955 1 Claim. (Cl. 18-54)This invention relates to a process for easily producing hollow viscoserayon filaments containing numerous independent small gas cells byviscose process. In the industrial process for producing hollow viscoserayon filaments of heretofore, sodium carbonate is added to viscose andit is necessary in general to prepare a special spinning bath such as abath of higher acidity or of higher zinc sulfate content than usualspinning bath, and further for viscose it is necessary to add specialsurface active agents or carbon disulfide or to make the degree ofripeness younger than usual process. Moreover, there are disadvantagesin that the filament produced contains gas cells irregularlydistributed, and sometimes the cells, being tubular form, have tendencyto be collapsed in subsequent procession to decrease the volume and alsoin that the strength and theelongation of the filament are low.

This invention is characterized in that the disadvantages as describedabove are eliminated and it has no necessity of using a spinning bath ofspecial composition. According to this invention, alkali solublecarbonates of the amount of 24% on the basis of viscose is dissolved inviscose and said viscose is spun at 9.0l1.5 of Hottenroth value in aconventional spinning bath of the composition of 911.5% sulfuric acid,18-25% sodium sulfate and 0.6-l.5% zinc sulfate at a temperature over 60C., thereby to produce hollow filaments of large volume having not onlystrength and elongation not inferior to the conventional filaments butalso containing uniformly distributed numerous independent small gascells. The invention will now be explained in the following withreference to the accompanying drawings wherein,

Figure 1 are enlarged side views of hollow viscose rayon filamentsproduced in accordance with this invention;

filaments of Figure 1;

Figure 3 are enlarged side views of filaments produced by conventionalprocess;

Figure 4 are enlarged cross sectional views of the filaments of Figure2; and

Figure 5 is a diagram showing the, domain where hollow filaments may beproduced.

The type of the filaments produced by the process of this invention isas seen in Figures 1 and 2, and has numerous independent gas cellsuniformly distributed therein and has a cross section like that of alotus rhizome. Its strength and elongation are also excellent, the wettenacity being 0.8 g./d. while the wet elongation over 20%.

It is of course possible to produce hollow filaments also by a processother than this invention at temperature lower than 50 C. of thespinning bath, but in such a case, it is necessary to make theconcentration of sulfuric acid higher than 13% or to make the zincsulfate content higher than 3%. Moreover the filament produced has gascells distributed irregularly as shown in Figure 2 are enlarged crosssectional views of the will be described.

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Patented May 20, 1958 Figures 3 and 4 and it is difiicult to produce ahollow filament of uniform quality, causing great uneveness in lustreand dyeing.

The conditions for producing hollow filaments are very delicate. On theextrusion of a viscose filament into a spinning bath, regeneratedcellulose film is firstly formed around the outside of the filament andacid diffuses through this film into the inside to mix with the materialtherein and, reacting-with sodium carbonate in the viscose, producescarbon dioxide, which forms gas cells since the evasion of the carbondioxide is prevented by the outside film. Accordingly the conditions ofthe distribution and the nature of the gas cells may be varied greatlydependingupon the condition and the rate of the formation of the outsidefilm as well as the condition and the rate of the diffusion of theliquor of the bath. If" the formation of the film is too slow or tooquick and a thick film is formed, the formation of gas cells may not beachieved or become very irregular even if they are formed.

As an example showing the above, employing the conventional viscosehaving 8% cellulose concentration and 6.3% total alkalinity and addedwith 2.8% sodium carbonate on the basis of the amount of the viscose,spinning is carried out in the conventional spinning bath containingl0.5-l0.7% sulfuric acid, 2023% sodium sulfate and 1% zinc sulfate, andchanging ,the temperature of the spinning bath and the coagulation value(Hottenroth value), the conditions of production of gas cells in afilament spun are illustrated in Figure 5. It is noted that gas cellsare'produced at the bath temperature over 60 C. with Hottenroth value inthe range 1010.5, but when the degree of ripeness of the viscose isincreased or decreased, it is necessary to raise the bath temperature inorder to obtain hollow filaments. The range of ripeness required forobtaining hollow filaments at the relatively low bath temperaturedepends upon the concentration of sulfuric acid of the spinning bath,and the higher the concentration is, the range of ripening moves toyounger side while the lower the concentration is, it moves to olderside. However, with Hottenroth value of higher than 11.5, it isnecessary to make the sulfuric acid concentration higher than 11.5% andthe size of gas cells produced becomes larger and the distributionthereof uneven to give undesirable result. On the other hand, withHottenroth value of less than 9.0, production of gas cells will belessened and therefore it is not desirable either.

When the amount of sodium carbonate added to viscose is increased ordecreased, the domain for producing gas cells may be increased ordecreased as a whole, while with sodium carbonate of less than 2.0% theproduction of gas cells is little even at the optimum domain for theproduction, while with the addition of sodium carbonate of more than 4%,the strength and the elongation of the filament is lowered although theproduction of gas cells is great and therefore neither of them isdesirable.

In the followings, some examples of this invention Example 1 Toconventional viscose having 8% cellulose and 6.3% total alkalinity isadded 2.5% sodium carbonate and is thoroughly dissolved. The viscose isripened to Hottenroth value 10.5, and is spun into yarn of deniercomposed of 30 filaments in a spinning bath containing 10.8% sulfuricacid, 22% sodium sulfate and 0.9% zinc sulfate at 63 C. with immersionlength of 60 cm. at spinning speed of 65 m./min. Hollow filaments asshown in Figures 1 and 2 are produced that has numerous independent gascells distributed therein and have cross sections like that of a lotusrhizome.

3 Its physical properties are as follows:

Dry tenacity g./d 1.8 Wet tenacity g./d 1.0 Dry elongation percent 24.8Wet elongation do 34.2

Example 2 3% sodium carbonate is added to the same viscose as in Example1 and the viscose is spun at Hottenroth value 11.0 in spinning bathcontaining 11.0% sulfuric acid, 21.5% sodium sulfate, and 1.2% zincsulfate at 65 C., and hollow filaments similar to those in Example 1 areobtained.

Example 3 To viscose is added 2.5% ammonium carbonate, and the viscoseis spun at Hottem'oth value 9.5 in spinning bath containing 10.2%sulfuric acid, 22% sodium sulfate, and 0.7% zinc sulfate at 66 C. andsimilarly hollow References Cited in the file of this patent UNITEDSTATES PATENTS 1,831,030 Picard Nov. 10, 1931 2,136,464 Picard Nov. 15,1938 2,476,293 Hall July 19, 1949 Hall Dec. 27, 1949

